1. Technical Field
The present disclosure relates to a capacitor structure and more particularly relates to a composite capacitor structure having a peak-valley like structure.
2. Description of the Related Art
More and more electronic devices are being required to be microminiaturized (light, thin, and small) with high efficiency. Thus, capacitor devices in electronic devices are being required to be small, have a large capacitance and have low impedance at high frequency bands. In practice, an embedded large capacitance capacitor device having low impedance at high frequency bands may be used to decrease noises from a power supply at the high frequency bands due to circuit switching at high speeds.
The capacitance (C) of the capacitor device may be expressed by the following equation:
      C    =          K      ⁢              A        d              ,wherein K is a dielectric constant (k value) of a dielectric layer, d is a gap distance between conductive materials, and A is an overlapped area between the conductive materials. Thus, to increase the capacitance of the capacitor device, the dielectric constant (K) of the dielectric layer or the overlapped area between the conductive materials needs to be increased, or the gap distance (d) between the conductive materials need to be decreased. However, due to material, process, and fabrication limitations, it is difficult to feasibly increase the dielectric constant (K) of the dielectric layer. Due to process and fabrication limitations, it is difficult to feasibly decrease the gap distance (d) between the conductive materials. Additionally, the overlapped area (A) between the conductive materials in conventional flat-type capacitor structures is not allowed of increasing significantly due to of flat substrate surface limitations. Thus, the capacitor device lacks sparking development in capacitance.
In the conventional technology, the embedded capacitor of the package or on the substrate may not achieve the effect of low impedance at high frequency. Therefore, the on-chip capacitor is usually utilized to inhibit noise at high frequency bands (GHz). However, the on-chip capacitor takes up a lot of chip space and some chip circuit designs do not allow enough space for on-chip capacitors. Meanwhile, to inhibit noise at middle to low frequency bands, a surface mount device (SMD) capacitor is utilized, since the embedded capacitor of the package or on the substrate also can not achieve large capacitance. Thus, a capacitor inhibiting noise in all frequency bands, having a large capacitance and low impedance is desired.